Pharmacokinetics of m-chlorophenylpiperazine after intravenous and oral administration in healthy male volunteers: implication for the pharmacodynamic profile.

INTRODUCTION: Serotonin plays an important role in psychiatric diseases, most notably in depression and anxiety. Seven different major serotonin receptor subtypes have been described. Receptor-selective agonists and antagonists have been searched for to find a suitable drug to test the in vivo receptor sensitivity. Different serotonin receptor subtypes take part in the control of neuroendocrine function. m-Chlorophenylpiperazine (mCPP) acts as an agonist to serotonin 2C, 1A, 1B, and 1D receptor subtypes and is applied in challenge tests. The object of this study was to develop a pharmacokinetic-pharmacodynamic model to describe the effects of mCPP on pituitary hormone secretion. METHODS: The hormone and mCPP plasma concentrations were determined after intravenous and oral administration of mCPP to 12 healthy men. The kinetic parameters of mCPP were compared to the drug's effect on hormonal response. RESULTS: After mCPP treatment, ACTH, cortisol, and prolactin levels were significantly increased compared to placebo. There was also a significant increase in clinical response (anxiety, shivering, dizziness, heightened sensitivity toward light and noise, and fear of losing control). Maximum mCPP concentrations varied 2.3-fold after intravenous infusion and 8-fold after oral administration. The absolute bioavailability ranged from 12% to 84%. mCPP's elimination half-life ranged from 2.4 h to 6.8 h after intravenous infusion and from 2.6 h to 6.1 h after oral application. However, the kinetic data as well as the pharmacodynamic response varied to an extent that precluded pharmacokinetic-pharmacodynamic modeling. The wide interindividual variability in mCPP's disposition kinetics could not be fully explained by genetic variation of the mCPP-metabolizing enzyme cytochrome P4502D6, which was determined in all probands. DISCUSSION: Other factors contributing to the variability in disposition kinetics could not be ruled out in this study, suggesting that mCPP is not a suitable model drug to test serotonin 2C receptor activity in vivo.

CYP2D6 polymorphism and tardive dyskinesia in schizophrenic patients.

Antipsychotic drug-induced tardive dyskinesia (TD) is a serious problem during psychopharmacologic treatment of schizophrenic patients. In search of genetic factors contributing to TD, there is a lack of consensus regarding the role of the polymorphic isozyme cytochrome P450 CYP2D6, which is involved in the oxidative metabolism of antipsychotic drugs. In the present case-control study, we tested the putative influence of the CYP2D6 genotype on the development of TD. Out of 157 patients, 109 were retrospectively selected meeting DSM IV criteria for schizophrenia or schizoaffective disorder, and 50 of them persistently presenting with TD. Genotyping detected the functional allele CYP2D6 *1, the known major defective alleles CYP2D6 *3, *4, *5, *6, and gene duplication. According to their number of functional CYP2D6 alleles, subjects were divided into carriers of none, one, or at least two functional CYP2D6 alleles. The proportions of these categories did not differ between patients and an ethnically homogenous control population (n = 195, p = 0.99) or between patients with and without TD (p = 0.818). Schizophrenic patients were carriers of gene duplication more often than healthy probands, without revealing statistical significance (p = 0.10). Out of seven patients with gene duplication, three developed persistent TD. Furthermore, patients with and without TD were comparable according to age, age of onset, gender, and duration of illness, but subjects with TD had taken more lifetime chlorpromazine equivalents (CPZ) than had patients without TD (chi 2-test, Student's t-test). Forward as well as backward logistic regression analyses confirmed that the presence of TD was influenced by lifetime CPZ but not by age, age of onset, gender, duration of illness, or CYP2D6 genotype. In contrast to the relevance of lifetime CPZ, the lifetime dose of antipsychotic drugs known to be metabolized by CYP2D6 did not significantly influence the presence of TD. In conclusion, our results provide no evidence for the contribution of CYP2D6 genotype to the development of TD in schizophrenic patients receiving long-term antipsychotic medication.

The insulin gene VNTR polymorphism in Alzheimer's disease: results of a pilot study.

Insulin (INS) and insulin-like growth factors include different polypeptides involved in growth and development. Possibly they play a role in the pathogenesis of neurodegenerative disorders such as Alzheimer's disease (AD). A variable number of tandem repeats (VNTR) polymorphism at the human INS 5'-flanking region consisting of three distinct allele classes has been shown to influence the tissue-specific expression of INS and the insulin-like growth factor 2 (IGF-2). Since alterations in the expression of INS or IGF-2 might be relevant in AD, we investigated the association between the INS VNTR polymorphism and the risk for AD. We found no association between the INS VNTR genotype and the risk for AD (p = 0.873). However, survival analysis revealed that class III homozygotes of the INS VNTR polymorphism had an earlier initial onset in patients suffering from early AD (p = 0.002). Our preliminary results suggest, that genetically determined alterations of the INS/IGF-2 metabolism might modify the course of AD. Further studies are warranted to confirm these data in larger study samples.

24S-hydroxycholesterol in cerebrospinal fluid is elevated in early stages of dementia.

The brain is the most cholesterol-rich organ in the human body. Accumulation of excess cholesterol in hippocampal neurons promotes the cleavage of the amyloid precursor protein (APP) into amyloidogenic components with the consequence of the acceleration of neuronal degeneration. Conversion of cholesterol to 24S-hydroxycholesterol mediated by cholesterol 24S-hydroxylase (CYP46) is the major pathway for the elimination of brain cholesterol and the maintenance of brain cholesterol homeostasis. We examined whether cerebrospinal fluid (CSF) 24S-hydroxycholesterol levels differ between patients with dementia, patients with mild cognitive impairment (MCI), and cognitively intact control subjects. Plasma and CSF concentrations of 24S-hydroxycholesterol and cholesterol in 32 patients with Alzheimer's disease (AD), 11 patients with vascular dementia, seven patients with MCI, and seven cognitively intact control subjects were measured by combined gas-chromatography/mass spectrometry. We show elevated concentrations of 24S-hydroxycholesterol in the CSF of AD patients and we interpret this finding as a consequence of increased cholesterol turnover in the central nervous system during neurodegeneration. The observed influence of the apolipoprotein E epsilon4 (APOE4) allele on CSF 24S-hydroxycholesterol concentrations with a gene-dosage effect suggests the existence of a link between the AD risk factor APOE4 and CNS cholesterol metabolism. The elevation of CSF 24S-hydroxycholesterol appears to occur early in the disease process, since patients with mild cognitive impairment had also increased CSF concentrations of this compound. We believe that the CSF concentration of 24S-hydroxycholesterol is altered in AD-related neurodegeneration and thus, CSF 24S-hydroxycholesterol may be a marker for monitoring the onset and progression of the disease.

Allelic variants of the serotonin(2C) receptor and neuroendocrinological responses to the serotonin(2C) receptor agonist m-chlorophenylpiperazine in healthy male volunteers.

The neurotransmitter serotonin (5-HT) possesses several receptors and their subtypes, some of which are polymorphic, such as the 5-HT(2C) receptor. The latter has been implicated in the control of neuroendocrine function, and has been discussed in the pathophysiology and pharmacotherapy of psychiatric disorders such as obsessive-compulsive disorder, panic disorder and bipolar affective disorder. To investigate whether the 5-HT(2C) receptor polymorphism contributes to the variation of neuroendocrinological responses elicited by activation of the hypothalamic-pituitary axis, we performed an m-chlorophenylpiperazine (m-CPP) challenge and monitored m-CPP and ACTH, cortisol and prolactin plasma levels in 16 healthy male volunteers carrying the common 5-HT(2C)-cys-23 receptor gene and 16 healthy male volunteers carrying the less frequent 5-HT(2C)-ser-23 receptor gene. The 5-HT(2C) polymorphism contributed little to the variation of the scores regarding hormonal responses of ACTH, cortisol and prolactin to the m-CPP challenge. The group carrying the rare 5-HT(2C)-ser-23 receptor gene showed a faster and stronger but not statistically significant ACTH response to the challenge. However, it is noteworthy that there is a 'medium' effect size of the ACTH response according to the conventions of Cohen, and thus comparable to other studies. Both groups show similar major scores in the Temperament and Character Inventory (TCI).

Influence of CYP2D6 genotype and medication on the sparteine metabolic ratio of psychiatric patients.

OBJECTIVE: To investigate the influence of CYP2D6 genotype and medication on the reliability of phenotyping in a naturalistic setting of psychiatric inpatients. METHODS: The phenotype of 160 psychiatric inpatients was estimated by taking the urinary metabolic ratio (MR) of the concentrations of sparteine to 2- and 5-dehydrosparteine. Genotyping identified CYP2D6*1, *3, *4, *5 and *6 alleles as well as duplication of the CYP2D6 gene. All subjects underwent detailed drug history including drug dose and therapeutic drug monitoring to control compliance and abuse of other psychotropic drugs. These data were compared with those of 195 unmedicated healthy Germans. RESULTS: The cumulative distribution of the MR in patients showed a significant shift to higher MR when compared with that of healthy subjects (P < or = 0.001). Patients medicated either with selective serotonin reuptake inhibitors (SSRIs, P < or = 0.001), antipsychotic drugs (P= 0.002) or other drugs known to be substrates or inhibitors of CYP2D6 (P < or = 0.001) showed a significantly higher mean MR than unmedicated patients. However, there was no significant effect of tricyclic antidepressants on the MR. Healthy subjects with CYP2D6 deficiency were separated by a MR of greater than 20 from those who expressed functional CYP2D6. Seven patients carrying at least one functional CYP2D6 allele revealed a MR of greater than 20, indicating the occurrence of phenocopying. CONCLUSION: The results of phenotyping may be falsified by drugs known to be substrates or inhibitors of CYP2D6; thus, this method is not sufficiently reliable. However, since we observed the phenomenon of phenocopying only in patients treated with a SSRI such as fluoxetine, fluvoxamine or paroxetine, we conclude that sparteine phenotyping of medicated patients detects CYP2D6 deficiency correctly, provided that patients treated with these SSRIs are excluded.

Serum levels and cardiovascular effects of tricyclic antidepressants and selective serotonin reuptake inhibitors in depressed patients.

Tricyclic antidepressants (TCAs) and selective serotonin reuptake inhibitors (SSRIs) are used to treat depression. Whereas cardiovascular effects have occasionally been reported during controlled studies with SSRIs, TCA treatment poses a well-known problem in this respect. To investigate the putative correlation between antidepressant dose or serum levels and adverse effects, the authors devised a naturalistic study to evaluate the tricyclic antidepressants' and SSRIs' effect on the cardiovascular system. The authors also compared antidepressant serum levels to adverse effects. Inpatients treated with TCAs or SSRIs were included; an electrocardiogram (ECG) and a Schellong test were carried out on the day patients entered the hospital and during steady-state treatment with antidepressant drugs when blood was drawn for therapeutic drug monitoring. The patient population consisted of 114 acutely depressed patients; 81 patients were treated with TCAs and 33 with SSRIs. The TCAs comprised amitriptyline (n = 43), clomipramine (n = 11), doxepin (n = 19) and imipramine (n = 8); the SSRIs comprised fluvoxamine (n = 14) and paroxetine (n = 19). In TCA-treated patients, the authors observed the same type of abnormalities in conduction and orthostatic hypotension as had been observed earlier. The authors also observed cases of first-degree atrioventricular block, prolonged QTc interval, and orthostatic hypotension in SSRI-treated patients. Thus SSRIs also appear to affect the cardiovascular system, which might pose a problem for patients with preexisting conduction disease. The authors observed a strong correlation between the decrease in systolic pressure and antidepressant serum concentration (except for clomipramine and paroxetine), suggesting that antidepressant serum level is a better correlate than dose.

Identical distribution of the alpha 2-macroglobulin pentanucleotide deletion in subjects with Alzheimer disease and controls in a German population.

Recently, an association between a deletion polymorphism in the alpha 2-macroglobulin gene (A2M) and Alzheimer disease (AD) has been reported. The aim of the present study was to corroborate this association in a German population of 102 AD patients and two control samples of 191 healthy subject and 160 depressed patients. The frequency of the A2M genotype in AD patients was almost identical to that in both control samples. Logistic regression analysis revealed an effect of age and the APOE genotype on AD risk, but no effect of the A2M genotype. Our findings do not support the fact that the previously reported positive association between A2M deletion polymorphism and AD modifies the disease risk in the studied population. Am. J. Med. Genet. (Neuropsychiatr. Genet.) 96:775-777, 2000.

No association of serum levels of interleukin-6 and its soluble receptor components with a genetic variation in the 3'flanking region of the interleukin-6 gene in patients with multiple sclerosis.

Interleukin-6 (IL-6) plays an important role in the regulation of the inflammatory response in multiple sclerosis (MS) and its animal model, experimental autoimmune encephalomyelitis (EAE). Previous reports indicated that a variable number tandem repeat (vntr) polymorphism in the 3'flanking region of the IL-6 gene (C allele) is associated with altered activity of IL-6 in vivo. Therefore, we analyzed the frequency distribution of IL-6 gene C allele vntr poymorphism in 96 MS patients and 106 ethnically matched healthy controls. Moreover, possible correlations between genotypic differences of IL-6 gene and serum levels of IL-6, soluble IL-6 receptor (sIL6-R), soluble gp130 (sgp130), soluble intercellular adhesion molecule-1 (sICAM-1) and soluble vascular cell adhesion molecule-1 (sVCAM-1) were investigated. There were no differences in the allelic distribution of the IL-6 gene C allele between MS patients and healthy controls, and no association of the IL-6 gene C allele with serum levels of IL-6, sIL-6R, spg130, sICAM and sVCAM-1 was found.

No association between an intronic biallelic polymorphism of the FE65 gene and Alzheimer's disease.

The cleavage of the amyloid precursor protein (APP) into amyloidogenic components (Abeta) is a central event in the pathogenesis of Alzheimer's disease (AD). FE65 is a protein that is involved in APP metabolism and may facilitate the production of Abeta. Recently, an intronic polymorphism of the gene encoding FE65 (FE65) was associated with altered risk for the development of sporadic AD. In our sample of 102 AD patients and 351 non-demented controls we did not replicate the association between FE65 and AD. Moreover, we observed no risk-modifying interaction and no linkage disequilibrium between FE65 and the gene encoding the acid protease cathepsin D (catD), which - like FE65 - is involved in APP metabolism and is also located on chromosome 11p15. We conclude that, whereas FE65 is implicated in AD pathology, the gene encoding FE65 does not appear to confer a substantial risk for AD.

Steady state concentrations of clomipramine and its major metabolite desmethylclomipramine in rat brain and serum after oral administration of clomipramine.

Twenty male Sprague-Dawley rats received five oral doses of clomipramine 20 mg/kg at 4-h intervals. The animals were decapitated 1, 2, 3, 5 and 12 h after the last dose for determination of clomipramine and desmethylclomipramine in serum and frontal cerebral cortex. Time dependent concentrations of clomipramine and desmethylclomipramine paralleled in serum and brain. Half-lives were similar in serum and brain with 7.8 versus 6.2 h and 5.5 versus 5.0 h for clomipramine and desmethylclomipramine, respectively. Absolute concentrations, however, were markedly higher in brain than in serum - 12.5 fold for clomipramine and 7.4 fold for desmethylclomipramine. The data indicate that serum and brain concentrations of clomipramine and its demethylated metabolite are rapidly exchanged between blood and brain. Assuming that blood and brain kinetics in man and rat are comparable, it is concluded that monitoring blood concentrations of clomipramine and desmethylclomipramine is a useful way to evaluate brain concentrations.

Allelic association between the D10S1423 marker and Alzheimer's disease in a German population.

Recently a full genome survey detected an allelic association between Alzheimer's disease (AD) and the D10S1423 marker on chromosome 10p12-14 (40 cM from the telomere). In this study we examined the D10S1423 marker in an ethnically homogeneous German population of 80 AD patients and two groups of controls, 168 healthy subjects and 149 depressed patients. The 234-bp allele of the D10S1423 marker showed a significant association with AD (P = 0.033). In conclusion, our results support that the D10S1423 marker is associated with an increased AD risk and provides further evidence for an AD susceptibility locus on chromosome 10.

Plasma 24S-hydroxycholesterol: a peripheral indicator of neuronal degeneration and potential state marker for Alzheimer's disease.

The conversion of brain cholesterol into 24S-hydroxycholesterol and its subsequent release into the periphery is probably an important step for the maintenance of brain cholesterol homeostasis. Recent findings suggest that plasma 24S-hydroxycholesterol may be elevated in Alzheimer's disease (AD) and vascular dementia at least at some stage of the disease, suggesting increased brain cholesterol turnover during neurodegeneration. We investigated whether plasma 24S-hydroxycholesterol concentrations depend on the severity of AD and on the apolipoprotein E (apoE) genotype. Severity of AD and inheritance of the apoE4 allele were independently associated with reduced plasma 24S-hydroxycholesterol/cholesterol ratios. The results suggest that the decrease of plasma 24S-hydroxycholesterol/cholesterol in severely affected AD patients is a peripheral marker for loss of cholesterol 24S-hydroxylase in the CNS. Inheritance of the apoE4 allele may be associated with increased apoE-mediated transport of brain cholesterol to the periphery or with decreased activity of the 24S-hydroxylase. Longitudinal studies will assess the validity of the ratio plasma 24S-hydroxycholesterol/cholesterol as a state marker for AD.

Confirmation of the association between bleomycin hydrolase genotype and Alzheimer's disease.

Bleomycin hydrolase (BH), a cysteine protease from the papain superfamily, is considered to be a candidate for the beta-secretase, which is presumably involved in the production of beta-amyloid peptide. The G/G genotype of BH was identified as a significant risk factor for the development of Alzheimer's disease (AD) in subjects not carrying the apolipoprotein E epsilon4 allele (apoE-epsilon4). However, this finding was recently challenged. We studied this polymorphism in a homogenous sample of German AD patients and controls. The over-representation of the G/G genotype in AD patients could be confirmed, however it was more pronounced in apoE-epsilon4 carriers. Additional studies should be undertaken to increase the confidence that the BH polymorphism is associated with AD and to explore the relationship between BH and apoE.

Association between an interleukin-6 promoter and 3' flanking region haplotype and reduced Alzheimer's disease risk in a German population.

Several studies have demonstrated that interleukin-6 (IL-6) is involved in the pathogenesis of Alzheimer's disease (AD). We previously reported on an association between the C allele of a variable number of tandem repeat polymorphism in the 3' flanking region of IL-6 gene (IL-6vntr) and delayed initial onset and reduced AD risk. A novel G/C polymorphism at position -174 in the IL-6 gene promoter (IL-6prom) has recently been identified and appears to influence the regulation of IL-6 expression. We examined this functional polymorphism in 102 AD patients and two control groups of 191 healthy subjects and 160 depressed patients. There was no evidence for an allelic association between IL-6prom polymorphism and earlier age of onset or risk of AD. However, haplotype analysis showed a strong linkage disequilibrium between IL-6vntr and IL-6prom and demonstrated an interaction between IL-6vntr and IL-6prom which modifies AD risk.

A genetic variation of cathepsin D is a major risk factor for Alzheimer's disease.

Cathepsin D (catD) is an intracellular acid protease possibly involved in Alzheimer's disease (AD)-related neurodegeneration through cleavage of amyloid precursor protein into amyloidogenic components. We studied whether an exonic polymorphism of the catD gene (C --> T [Ala --> Val] transition at position 224), which possibly influences pro-catD secretion and intracellular maturation of the enzyme, was associated with the risk for the development of AD in 127 demented patients and 184 controls. The catD*T allele was significantly overrepresented in demented patients (11.8%) compared with nondemented controls (4.9%). Carriers of the catD*T allele had a 3.1-fold increased risk for developing AD than noncarriers. Carriers of the apolipoprotein E (ApoE) epsilon4 allele (ApoE*4) had a 3.9-fold increased risk than non-carriers. The adjusted odds ratio for subjects with the ApoE*4 and the catD*T allele was 19.0 compared with subjects with neither of these two alleles. Our data confirm the results of a recently performed pilot study in an independent sample and suggest that the catD genotype is strongly associated with the risk for AD.

Plasma 24S-hydroxycholesterol (cerebrosterol) is increased in Alzheimer and vascular demented patients.

Alzheimer's disease (AD) is characterized by the presence of senile plaques, neurofibrillary tangles, and neuronal cell loss associated with membrane cholesterol release. 24S-hydroxycholesterol (24S-OH-Chol) is an enzymatically oxidized product of cholesterol mainly synthesized in the brain. We tested the hypothesis that plasma levels of this oxysterol could be used as a putative biochemical marker for an altered cholesterol homeostasis in the brain of AD patients. Thirty patients with clinical criteria for AD, 30 healthy volunteers, 18 depressed patients, and 12 patients with vascular dementia (non-Alzheimer demented) were studied. Plasma concentrations of 24S-OH-Chol were assayed by isotope dilution;-mass spectrometry, cholesterol was measured enzymatically, and apolipoprotein E (apoE) was genotyped by polymerase chain reaction and restricted fragment length polymorphism. The concentration of 24S-OH-Chol in AD and non-Alzheimer demented patients was modestly but significantly higher than in healthy controls and in depressed patients. There was no significant difference in the concentrations of 24S-OH-Chol between depressed patients and healthy controls nor between AD and non-Alzheimer demented patients. The apoE straightepsilon4 allele influences plasma 24S-OH-Chol. However, this influence could be completely accounted for by the elevated plasma cholesterol in apoE4 hetero- or homozygotes. Plasma 24S-OH-Chol levels correlated negatively with the severity of dementia. AD and vascular demented patients appear to have higher circulating levels of 24S-OH-Chol than depressed patients and healthy controls. We speculate that 24S-OH-Chol plasma levels may potentially be used as an early biochemical marker for an altered cholesterol homeostasis in the central nervous system. 24S-hydroxycholesterol (cerebrosterol) is increased in Alzheimer and vascular demented patients.